Polygonal multiple tube system



April 3, 1956 c. J. STARNER ETAL 2,740,848

POLYGONAL MULTIPLE TUBE SYSTEM Filed Jan. 4, 1954 3 Sheets-Sheet 1 Z? II var/0r 7 i 73 fig -1 5 I I 7 (72 t ATTOR NE 1 April 3, 1956 c. J.STARNER ETAL 2,740,848

POLYGONAL MULTIPLE TUBE SYSTEM Filed Jan. 4, 1954 3 Sheets-Sheet 2INVENTORS CHAIFLES Smxwzz FKA/VKl/IV E, 721M465 ATTORNEY April 1956 c.J. STARNER ETAL 2,740,848

POLYGONAL MULTIPLE TUBE SYSTEM Filed Jan. 4, 1954 3 Sheets-Sheet 3INVENTORS cHA/FZES J Saw/v54; f /FANKu/v E. ZZLMAGE MW-M 11 TTOR NE Y2,740,848 POLYGONAL MULTIPLE TUBE SYSTEM Charles J. Stamer, Haddonfield,and Franklin E.Talmage, Westmout, N. 1., assignors to Radio Corporationof America, a corporation of Delaware Application January 4, 1954,Serial No. 402,112 25 Claims. (Cl. 179-171) structed by arranging aplurality of vacuum tubes in circular fashion in annular re-entrantinput and output cavities. At higher frequencies, annular cavitiescommon to a plurality of vacuum tubes may not be suitable because thevolumes of the cavities become too great to achieve the desiredfrequency of operation. The inherent internal capacitances of theplurality of vacuum tubes require that the volume of the cavities besmaller than can actually be obtained with the geometry ofannularcavities. It is therefore a general object of this invention toprovide a multiple tube system including resonant cavities having aconfiguration enabling operation at higher frequencies than haveheretofore been possible.

It is another object of this invention to provide a.

multiple tube system including polygonal resonant cavities whichinherently suppress undesired circulating modes of oscillation. t

It is another object to provide a multiple tube resonant cavity systemwhich is less expensive to manufacture than previously known systems andwhich utilizes flat metallic sheets.

It is a further object to provide a multiple tube system includingimproved means for tuning the input and output circuits over a widerange of frequencies. A still further object of the invention is toprovide a novel multiple tube system having a geometry enabling thecharging current flowing thru the tube seals to be more uniformlydistributed around the peripheries thereof so that the heating of theseals is reduced.

In one aspect, the invention comprises an amplifier including aplurality of electron discharge devices or vacuum tubes electricallycoupled in parallel thru the medium of a complex, generally polygonalphysical structure. The invention will be described, by Way of example,as having a generally pentagonal input cavity and a gen-' erallypentagonal output cavity, and having five vacuum tubes operativelydisposed in the two cavities. The elements of the physical structurewill be described in their relation with a metallic horizontalpentagonal separation plate separating the input cavity therebelow fromthe output cavity thereabove. The'structure is generally symmetricalabout (though not a figure of revolution about) an imaginary verticalcenter line passing thru the center of the horizontal pentagonalseparation plate. p 7 Five vacuum tubes are located in five circularapertures at the five corners of the pentagonal separation plate. Thetubes extend down'into'the inputcavityandf up into the output cavity.The input cavity is in the form of a'pentagonal prism coextensive withthe pentagonal separation plate and having a coaxial pentagonalreentrant member which may be adjusted axially to vary the volume of theinput cavity. The pentagonal re-entrant member is arranged relative tothe pentagonal separation plate so that the five corners of one areopposite thefive sides of the other. A coaxial input line includes acenter conductor. connected .to the center of the separation plate andan outer. conductor connected to'a circular aperture in the re-entrantmember. An adjustable impedance matching device is incorporated in theinput coaxial line.

The output cavity is formed between the metallic sepa-' ration plate anda larger parallel pentagonal metallic output plate spaced thereabove.The respective sides of the pentagonal separation plate and thepentagonal output; plate are parallel. A fixed coaxial pentagonalre-e'ntrant structure extends thru the output plate into the outputcavity. The corners of the pentagonal re-entrant structure are oppositethe sides of the pentagonal output plate. An output coaxial lineincludes a center conductor connected to the. separation plate and anouter conductor connected to the edges of a circular aperture in thereentrant structure. An adjustable impedance matching device isincorporated in the output coaxial line. Five adjustable coaxial lineshorted stubs are connected thru the re-entrant structure to the outputcavity to serve as shunt inductors which are variable to adjust theoutput coupling consistent with the bandwidth requirements.

' All points along the periphery of the pentagonal output cavity are incommunication with a downwardly extending transmission line, and allpoints along the inner edge of the output cavity adjacent the re-entrantstructure are in communication with an upwardly extending coaxialtransmission line. The downwardly extending, and the upwardly extending,transmission lines together constitute an output tuning lineelectrically a half wave length. The downwardly extending transmisisonline is formed between an outer pentagonal prismatic wall connected tothe outer edge of the pentagonal output plate, and a uniformly spacedinner pentagonal prismatic wall connected to the outer edge of thepentagonal separation plate. The upwardly extending transmission line isformed between-an outer pentagonal prismatic wall connected to apentagonal aperture in the pentagonal output plate, and a uniformlyspaced inner pentagonal prismatic wall connected to the outer edge ofthe pentagonal re-entrant structure. ,The efiective lengths of the twolines are adjustable by moving shorting bars axially between the innerand outer walls of the respective lines. The anodes of thefive vacuumtubes the pentagonal plate, the controland screen grids are,

input platen V 1 These and other objects and aspects of the inventionwill appear from a reading of the following more detailed Referring'nowto the' drawings for description of a 7 section corresponding to thatshown in Fig. 4 and showing the parts in a different ad-.justable'position.

five tube amplifier accordingto this invention, a separation plate formsa partition between an input cavity 11 and an output cavity 12. Theseparation plate 10 is pentagonal in shape and has five circularapertures near the five corners to receive five tetrode' vacuumtubes orelectron discharge devices 13 which may'be RCA type 6166 tubes. Thecontrol grid contact ring 14 of each of the tubes '13 is contacted by:spring fingers "15 which have areas separated from the separation plateltl'by mica dielectric plates'16. The control grids ofthetubes are thuscapacitively coupled to the separation plateltl. The screen' gridcontact ring 17 of each of"the"tubes 13 is similarlycapacitivelv-coupled to the separation plate 10 thru spring fingers 18and mica dielectric plates The input cavity 11 is formed between theseparation plate 10 and parallel spaced coextensive input plate 20. Theinput plate 20 has a pentagonal aperture thru which a pentagonalreentrant member"21*extends into'th'e input cavity 11. The fiveperipherab sides of'the pentagonal input cavity 11' are closedbyfivevertical 'plates'22 to form a pentagonal prismatic wall. The walls22"ext'eiid downwardly from the 'input plate 29 "for reasons which willappear as the description'proceeds. The input plate 20 is provided "withfive rectangular wells 24 having springsockets 25 receptive tothefilament prongs 26 of the'tub'es 13; The tube filaments arecapacitively coupled 'to 'the input plate 20 thru sockets 25; anddielectric sheets 27 to the walls of the wells 24 in the input plate 20.An input coaxial- 1ine'29 is connected thru an adjustable impedancematching device 30 to the input cavity 11, the center conductor'80 beingconnected thru conductors 77 and 31 to the center of the separationplate 10, and the'outer conductor 87 "being connected thruslidingcontacts': 88,1'0i21l3blfi member 85 and contacts 32 to acylindrical depending fl'ange 33 forming a part of the re-entrant"member 21." The reentraut member 21 includes'a circular aperture 34providing communication from the input impedance match ing device 30 tothe interior of the input'cavity 11'. "T he re-entrant member 21 isreciprocable along 'the'vertical axis of the system by means of fiveinput'cavity tuning rods 35, one of which is visible'in Fig. land'all'of which are shown by dotted line circles in Fig. 2.' The"tuning rods 35 are moved axially in unison to vary the position of there-entrant member 21 and thus vary" the volume or tuning of the inputcavity 11; Contact is maintained'between the re-entrant member 21 andthe input plate 20 by means of sliding contacts 36. it i It will benoted by reference to Fig. 2 that the peripheral edge of thte inputcavity 11 is formed by the pentagonal prismatic walls 22, and that theinner edge of the input cavity 11 is primarily'determined' bythepentagonal prismatic walls 37*of. the: re entrant member '2ll Itwillalso be noted that the pentagonal walls 22 and the pentagonal walls 37are'oriented in such a way that the angles or corners of one. areradially'opposite the s des of the other. It will further be notedthat'the five vacuum tubes are positioned between the five corners ofthe walls 22 and the five sides of the walls 37L By this construction,the volume within the input cavity 11 is suflicieiitly small sothat'the'cavity will resonate at very high frequencies. Theconstruction, being such as to include numerous angles, inherentlyattenu'ates'any undesired circulating modes of oscillation which mightotherwise be present. It will'be understood, that' the input cavity 11is primarily defined in the horizontal plane by the pentagonal prismaticwalls 22 and 37. However, the area between the re-entrantmernb'er 21 andthe separation plate 10 is also part of the input cavity 11. Inputenergy is supplied to cavity 11 frdni input coaxial line 29 through thecircular aperture 34fand the impedance matching device 30. l I; "I

The output cavity 12 will now be described w i th re:

erence to Figs. 1 and 3. In Fig. 3 theoutlipe of, the

pentagonal separation plate 10 is shown by a dotted line 22. The outputcavity 12 is formed between the separation plate 10 and a pentagonaloutput plate 40 which is in parallel spaced relationship above theseparation plate 10. The output plate 40 has pentagonal peripheral edgesparallel with, and extending beyond the edges of the separation plate10. A downwardly extending pentagonal prismatic wall or skirt 41 isconnected to the peripheral edge of output plate 40. The pentagonalprismatic wall 41 is equally spaced on all sides from the pentagonalprismatic wall 22 to provide therebetween five rectangular volumesconstituting a transmission line within which five rectangular shortingbars 43 (Figs. '1 and 2) are reciprocable. Metallic shorting bars 43 aremaintained in electrical contact with walls 22 and 41 by means ofsliding contacts 44 and 45. The five shorting bars 43 are moved inunison by means of five tuning rods 46, one of which is shown in Fig. 1and allofwhich are shown by dotted line circles in Fig. '2. "Referringto Figs. 1 and 3, a fixed re-entrant structureextends into the outputcavity 12. The re-entrant structure eomprises'a pentagonal base plate 48having its "peripherycoiinected to a pentagonal prismatic wall 49. Thefixed re-entrant structure 48, 4 9 is maintained in spaced relation withthe separation plate 10 by means of insulators 50, one of which is shownin Fig. 1. The output'plate 40 has a pentagonal aperture, the edge ofwhich is connected to apentagonal prismatic wall or skirt5 2 extendingupwardly in equally spaced relationship surrounding the pentagonalprismatic wall 43 of the re-entrant structure 48, 49. The fiverectangular volumesenclosedbetwee'n the walls 49 and 52 constitutinga"tran'smission line are closed at the top by means of five rectangularmetallic shorting bars 53 having contact fingers 54 and'55 slidablyengaging the walls 52 and 49, respectively. The rectangular shortingbars'53 are moved in unison by five adjusting rods 56, one of which isvshown in Fig. l, and'all of which are shown in Fig. 3.

- apparent that the output cavity 12 is in communication at itsperiphery with a downwardly-extending'tuning line formed between thepentagonal prismatic walls 22 and 41, and that the inner portions of thecavity 12 are in communication with an upwardly-extendirig tuning lineformed between the pentagonal prismatie Walls"49 and 52/ The distancefrom the lower shorting bars 43 to the upper shorting bars 53 iselectricallya half wave in length at the mean operating frequency'. 1The output cavity 12 is thus tuned by varying in unison, all of-theshorting bars 43, and/or varying in unison all of the shorting bars 53.

' It 'is thus far Electrical energy is taken from the output cavity 12by'means of an output coaxial line having a center conductor 58connected'to-the separation plate 10, and having an outer'conductor 59connectedto the edge of a circular aperture in the base plate 48 of there -entrant structure 48, 49. It is apparent that the output cavity 12is in communication with the space between the coaxial output conductors58' aiid'59 thru the space between the separation plate' 10 and the baseplate 48 of the re entrant structure 48, 49'. Technically, the spacebetween theplates 10 and 48 is'a part of'the output cavity 12;

The output plate '40 is provi'ded with five circular apertures atthefive corners to receivethe five vacuum tubes 13, As shown in Fig. l,the anode contact ring 61 of each of tubes'13 makes';electrical contactwith spring fingers 62 which are spaced from the output plate 44) bymeans of dielectric mica -sheets 63.

It will be noted-by' reference to Fig. 3 that the pentagonal prismaticwalls '22 and 41 defining the outc edge of thefoutput. cavity 12 arerelated with the pentag'tinal prismatic walls 49. and 52 defining theinner edge of the output cavity 12 in such a way as to minimize thevolune'within the output cavity 12. The inner iti l ter. pi i agd al wallsare arranged so that the i'slfi Iqiicornersoii one are opposite thesides of the b hat- B 't i a ang men the put-.- vi y. can be tuned to ahigher frequency than would otherwisebe possible while employingtubes-of a given power rating or size.

Five adjustable coaxial line shorted stubs are connected thru the re-entrant structure to the output cavity 12 to serve as shunt-inductorswhich may be adjusted for that degree of output coupling which isconsistent with the bandwidth requirements. Each coaxial line shortedstub consists of a-center conductor 65 connected to the separation plate10, and an outer conductor 66 connected to the edge of a circularaperturein the base plate 48 of the re-entrant structure 48, 49. It willbe noted from Fig. 3 that the shorted stubs 65, 66 are placed in thecorners of the re-entrant structure-48, 49' and outside the central areaof the re-entrant structure which is occupied by the coaxial output line58, 59. This con struction is such as to further a primary object ofthis invention which is to amplify high power radio frequency energy atvery high frequencies. N

The effective or electrical length of each of the shorted coaxial stubs65, 66 is adjustably determined by the position'of a shorting ring 68connected by a cradle 69 to an adjusting rod 70. together the conductors65 and 66 at the location of the rings. Axial movement of the adjustingrods 70 varies the shunt inductance coupled to the output cavity 12. Theshunt inductors are adjusted to provide that degree of'overcoupling fromthe output cavity 12 to the out- 7 which results in the desired;

put coaxial line 58, 59 H frequency response characteristic over thebandof frequencies being amplified.

Included within the output coaxial line 58, 59 is animpedance matchingdevice in .the form of a discontinuity in the coaxial line which may beadjustedin positionalong 'the line. The impedance matching deviceconsistsof a cylindrical sleeve 70' around and. spaced from the centerconductor 58 by means ofapertured discs 71 and- 72. Sliding electricalcontact'is'maintained between the peripheral edges of discs 71 and 72 bymeans vofsliding metallic spring contacts 73. The assembly .is movablealong the coaxial output line, by means ofa rod 74 .ex-

tending thru a longitudinal slot .75 in the/outer conductor 59. Thedevice is positioned about}: half wavelength from the output cavity 12and is adjusted so that the circuit formed by the discontinuity-and thelength of the coaxial line is electrically resonant, giving. animpedance transformation which results in a pure resist-. ance at theseparation plate 10.

Referring now to Figs. 1 and 4, the input impedance matching devicegenerally designated 30 consists of two fixed inner conductors 77 and 78both connected at 79 Ring 68 directly connects to the center conductor80of the input coaxial line 29.

Both of the inner conductors 77 and. 78 are connected at their oppositeends to the separation plate 10, thru conductive members 81 and31.

The impedance matching device 30 also includes two. I

outer conductors 82 and 83 both connected at their lower ends to anannular flange 84 extending inwardly from.

a metallic cylinder 85. ,Theltop ends of the outer conductors 82 and 83are similarly'connected thru an annular flange 86 to the metalliccylinder 85. The outer conductors 82 and 83, and the cylinder arerotatable as a unit. 'The lower end of cylinder 85 is maintained inelectrical contact with the outer conductor 87 of the input coaxial line29 by means of spring contac'ts88,

and the upper end of cylinders 85 is maintained in elec-' trical contactwith the depending flange 33 of the input re-entrant member 21 by meansof spring contacts 32.

The'outer conductors 82 and 83 may be rotated relative to the innerconductor 77 and 78 by rotating the cylinder 85.' When the outerconductors and cylinder are rotated 90 degrees from the position shownin Fig. 4, theparts-bear the relative relationships shown in Fig. Whenthe inner-and outer conductorsbear the' relationship shown in Fig. 4,the capacitancefabetweenm tively narrow band of component frequencies.

6 the- -inner and-outer conductors is a maximum; 'and when the parts arein the positions shown in Fig. '5, the capacitance; is a minimum. Theinner conductors may be positioned anywhere between the two extremesshown in Figs. 4 and 5.

The five vacuum tubes 13 are each supplied with operating potentials asfollows: The secondary coil 90 of a filament transformer 91 is connectedthru leads 92 to the spring sockets 25 engaging the filament prongs 26of the tube 13. The leads 92 are by-passed to ground at a distance of aquarter-Wavelength from the tubes so that the secondary coil 90 oftransformer 91 is at ground potential so far as the radio frequenciesare concerned.

The control grid contact ring 14 on tube 13 is connected thru springcontacts 15 thru a lead 93 to the negative terminal E0 of a source ofunidirectional potential. A bypass capacitor 94 is connected to groundat a point a quarter wavelength from the tube. The screen grid contactring'17 of tube 13 is connected thru spring contacts 18 and a lead 95contained in -a shielding tube (not shown) to the positive terminal 96of a source of unidirectional screen grid potential. The lead 95 is alsobypassed to ground at a point a quarter wavelength from the tube. Theanode contact ring 61 of tube 13 is connected thru spring contacts 62,lead 97 and plate resistor 98 to the 13+ terminal of a source ofunidirectional potential. The line 97 is by-passed to ground at aquarterwavelength from the tube.

The five tube amplifier shown and described herein by way ofillustrating the invention, is capable of providing I 50 kilowatts ofradio frequency output peak power at any frequency in the range between174 and 216 megacycles. This frequency range includes channels 7 thru 13in the very high'fr'equency television broadcasting band presentlyemployed in the United States. Ten kilowatts of radio frequency energyto'be amplified is applied thru the input coaxial line 29 to theamplifier. The input energy applied to the amplifier maybe that obtainedfrom a standard 10-kilowatttelevision transmitter. The amplifier isdesigned to amplify television picture signals having fre-. quencycomponents extending over a band which, according to present standards,is 4.5 megacycles wide. The sound signals of a television broadcast arenormally amplified in a separate amplifier designed to amplify a rela-The amplified sound signals are normally combined with the amplifiedpicture signals in a diplexer or filteiplexer from which the combinedsignal is applied to a radiating antenna.

In the operation of the multi-tube amplifier of this invention, radiofrequency input energy is applied thru theinput ,coaxial line 29 andthru the input impedance matching device 30 to' the input cavity 11. Theinput cavity '11 is tuned by adjusting its volume to the particularfrequency being amplified. This adjustment is made by moving the inputre-entrant member 21 thru the medium of the five tuning rods '35 untilthe input cavity 11 is tuned to the desired frequency. The outerconductors 82 and 83 of the input impedance matching device 30 arerotated relative to the fixed inner conductors 77 and 78 to a positionwhich provides the optimum impedance match, between the input line 29and the input cavity 11. This position is found by minimizing themeasured standing wave ratio on line 29. The tuning adjustment(re-entrant member 21) and the impedance matching adjustment (device 30)are mutually dependent and are mutually varied to minimize the standingWave ratio on input line 29.

The energy within the input cavity 11 is applied between the controlgrids and filaments of the five amplifiervacuum tubes 13. The amplifiedradio frequency energy appears between the anode electrodes and thescreen grid electrodes of the five tubes 13 from whence it is coupledtothe output cavity 12. The output cavity 12 is tuned to the frequencybeing amplified by adjusting the effec- .tive length ofthe doubleendedoutput' tuning wave line which is definedby coaxial inner and outerpentagonal prismatic walls. The ettective length of the outputtuningline is adjusted by moving the five shorting bars 43 inunison at thelower end of the guide, and/or moving the five shorting bars 53 inunison at the upper end of the tuning wave guide. The output cavity 12is tuned to the desired frequency when the eifective electrical distancefrom the lower'shorting bars 43 to the upper shorting bars 53 is a halfwavat the desired mean frequency of operation. The double ended line isthe means by which the anode circuit of the amplifier is tuned.

Energy. from the output cavity 12 is coupled to the output coaxial line58, '59. The coupling between the output cavity 12 and the outputcoaxial line is optimized by adjusting the five shunt inductors. Theshunt inductors are in the form of shorted coaxial stubs each includingan. inner conductor 65 and an outer conductor 65. The eifective lengthof each shorted stub is determined by, the position ofthe. shortingring, 68 slideably located between the inner conductor 65 and: the outerconductor 66, They shunt inductors are adjusted to. provide that degreeof. overcouph'ng between. the output cavity 12 and the output coaxialline, 58, 59, which results in the. desired broadband-passcharacteristic.

An output impedance matching device. 70', 71, 72 forms a discontinuityin the coaxial output line 58, and its position along the line may beadjusted to tune the secondary circuit; formed by the length of outputline between theseparation plate and the discontinuity. The impedancematching device is normally positioned at a distance of approximately ahalf-wavelength from the output cavity 12, and its exact position isadjusted thru the medium of the adjusting rod 74 extending thru a slot75 in the outer conductor 59. of the output coaxial line.

The polygonal. multiple, tube system of this invention has been shownand described in the form of an amplifier. It will, of course, beunderstood that the teachings of this invention are not limited. toamplifiers, but are applicable to oscillators and other forms oftranslating circuits as well. to peritagonalarrangements, but is alsoapplicableto other polygonal arrangements What is claimediisi 1Q Aresonant cavity having a volumein the geometricalform of a polygonalprism with a coaxial polygonal prismatic aperture therein, said prismand said aperture having an equal number of sides, said prism and saidaperture being oriented so that the corners of one are opposite thesides of the other.

' 2. A resonant cavity as defined in claim 1 and in addition a vacuumtube electrically coupled thereto and physically disposed at leastpartially within said cavity between a corner of said prismjand anadjacent side. of said aperture. j

3. The combination of a resonant cavity having a volume, in the form ofa polygonalprism ofn sides with. a coaxial prismatic apertureof nsidestherein, said aperture being oriented relativeto the prism so thatthey corners of one are opposite the sides of the other, and n electrondischarge devices electrically coupled thereto and physically disposedbetweenthen cornersof said prism and the n sides of said aperture.

4. A resonant cavity having a volume in the geometrical form ofapolygonal prism with a coaxial polygonal prismatic re-entrance therein,said prism and said reentrancehaving an equal number of sides, saidprism and said re-entranoe beingdisposed with theacorners of. oneopposite. the sides oi the other.

5. A resonant cavity as defined in claim 4., and in addition an electrondischarge device electrically. coupled theretov and physically disposedat least partially within.

said. cavity between. a, cornerof said prism .and an adjacent sideofsaid re-entrance,

6, The, combination. of, a resonant .cavity. havinga. ,vvol-t Obviously,the invention is not limited time in the form of a polygonal prism oi nsides with a coaxial prismatic rc-entrance of it sides therein, saidreentrance being oriented relative to the prism so that the corners ofone are opposite the sides of the other, and n vacuum tubes electricallycoupled to said resonant cavity and physically disposed between the ncorners of said prism and the n sides of said re-entrance.

7. A resonator system comprising first and second spaced polygonal endplates connected at their peripheries by sidewalls to define a polygonalprismatic cavity, said first end plate having a polygonal aperturetherein, said polygonal end plate having the same number of sides assaid polygonal aperture therein, the corners of one being opposite thesides of the other, a polygonal prismatic re -entrant member disposed insaid polygonal aperture, said re-entrant member having a circularaperture therein, and a coaxial line having an outer conductor connectedto the edge ofsaid circular aperture, and having an inner conductorconnected to said second end plate.

8. A resonator system asdefined in claim 7 wherein said polygonalprismatic re-entrant member is axially movable'to vary'the' volumewithin said cavity.

9. A resonator system as defined in claim 7, and in addition, aplurality of electron discharge devices electrically coupled to saidcavity and physically disposed in said cavity between said sidewalls andsaid reentrant member.

10. A resonator system as defined in claim 7, and in addition, aplurality of electron discharge devices electrically coupled to saidcavity and physically disposed in said cavity in the spaces between thecorners formed by said sidewalls and the sides of said polygonalre-entrant member.

11'. A resonator system as defined'in claim 10 wherein said polygonalprismatic re-entrant member is axially movable to vary the volume ofsaid cavity.

12. A resonator system comprising first and second spaced polygonal endplates, said second end plate having a polygonal aperture therein, theedges of said aperture beingopposite the peripheral edges thereof, apolygonal prismatic re-entrant member having sidewalls and a base plateextending into said polygonal aperture, a polygonal skirt connected atone end to the polygonal aperture in said second end plate in equallyspaced relationship around the sidewalls of said re/entrant structure,said skirt and the sidewalls of said re-entrant structuredefiningtherebetween a tuning line in communication with the cavitybetween said first and second end plates, and two polygonal coaxialspaced skirts having corresponding ends connected respectively to theperipheral edges of said first and second end plates to definetherebetween a second tuning line incommunication with the cavitybetween said fii st. and second end plates.

13-. A resonator system as defined'in claim 12, and in addition, aplurality of electron discharge deviceselectrically coupled to saidcavity, and physically disposed in thecavitybetween said first andsecond end plates.

14. A resonator system as defined in claim 12, and in addition,shortingmeans in said'tuning lines to determine the effective electricallengths thereof.

15. A resonator system as defined inclaimlZ, wherein said base plate ofsaid re entrance structure has a circular aperture, and in addition, acoaxial line having an outer conductor connected to the edge of saidcircular aperture, and having an inner conductor connected to saidfirstend plate.

16 Areson'ator system as def ned in claim 15 wherein said baseplateofsaid re-entrant structure includes a second circular aperture, and inaddition, a coaxial line tuning stub including-an outer conductorconnected to the edgeof said secondcircular aperture,- and including acenter conductor connected to said first end plate.

17. A resonatorsystem as;d efined in claim 16, and in addition; meanstoyarycthe etiective-electrical. length of said ,tuningstub'.

relation therewith, said input 18. A multiple tube system comprising apolygonal separation plate, a polygonal input plate in parallel spacedplate being provided with a polygonal aperture, a polygonal prismaticre-entrant member extending thru said polygonal aperture, sidewallsconnecting the peripheral edges of said separation plate and said inputplate, whereby a polygonal input cavity is formed, said re-entrantmember having a circular aperture, a coaxial line having an outerconductor connected to the edge of said circular aperture and having aninner conductor connected to said separation plate, a polygonal outputplate in parallel spaced relation on the opposite side of saidseparation plate, said output plate being provided with a polygonalaperture, a polygonal prismatic re-entrant structure disposed withinsaid polygonal aperture, an enclosure connecting the peripheral edges ofsaid output plate and said separation plate, whereby to form an outputcavity, said re-entrant structure having a circular aperture, and anoutput coaxial line including an outer conductor connected to saidcircular aperture and an inner conductor connected to said separationplate, and a plurality of electron discharge deviceselectrically coupledto said input and output cavities and physically disposed therein.

19. A multiple tube system as defined in claim 18, and in addition, apolygonal prismatic tuning line in communication with said outputcavity.

20. A multiple tube system as defined in claim 18, and in addition, aplurality of coaxial line shorted stubs coupled thru said re-entrantstructure to said output cavity.

21. A multiple tube system as defined in claim 18, and in addition, animpedance matching device operatively connected between said inputcoaxial line and said input cavity.

22. A multiple tube system as defined in claim 18, and in addition, anadjustable impedance matching device positioned within said outputcoaxial line.

23. A radio frequency translating device comprising, a plurality ofelectron tubes disposed in a circle about an axis, said tubes havinginput and output electrodes, a

I first cavity resonator common to and electrically cou- 24. A radiofrequency translating device as defined in. claim 23 wherein each ofsaid cavity sections have an axis common with said axis about which thetubes are disposed.

25. A radio frequency translating device as defined in claim 23 whereinat least one of the cavity sections of each of said first and secondcavity resonators is adjustable in axial length to tune the respectiveresonator.

References Cited in the file of this patent UNITED STATES PATENTS2,473,777 Belchlyn June 21, 1949 2,487,619 Usselman Nov. 8, 19492,554,501 Preist May 29, 1951 2,562,323 Martin July 31, 1951 2,565,113Baker Aug. 21, 1951

